The present invention relates generally to vehicle engines, and more particularly to piston pins.
In internal combustion engines, the bottom ends of the piston rods are coupled to a crankshaft and the top ends are coupled to respective piston crowns such that linear reciprocating motion of the piston crowns is converted to rotational motion of the crankshaft. Accordingly, the top ends of the rods must be coupled to the piston crowns, which move in only a single degree of freedom, in such a way that permits the bottom ends of the rods to move in two degrees of freedom.
The key mechanism in coupling a piston rod to a piston crown is the piston pin, which passes through a piston skirt and piston crown and continues on through the piston rod. By means of the piston pin, the piston crown and the piston rod are firmly joined together. It will be readily appreciated that the failure of a piston pin could result in misalignment and/or separation of these components, which could cause severe engine damage.
It happens that piston pins ordinarily are held with metal clips, which can fail. Accordingly, as recognized herein, it is desirable to provide a means for holding the piston pins in engagement with the piston rod. The present invention further understands that this can be accomplished using piston plugs that are inserted into the pins, but that it is possible for the plugs to shake loose from the pins during operation, thereby potentially causing damage to the engine. The present invention understands that simply gluing the plugs to the pins would be less than effective, because the adhesive could potentially lose its effectiveness in the harsh engine environment. Accordingly, the present invention provides the solutions disclosed herein to retain plastic piston plugs in piston pins.
A piston pin assembly includes a hollow piston pin defining first and second ends. A first pin plug is disposed in the first end and a second pin plug is disposed in the second end. A rod interconnects the plugs.
In a preferred embodiment, each pin plug includes a head disposed outside the piston pin and a stem disposed within the pin. In a first embodiment, the stem of each pin plug can be solid, and both the stems of the pin plugs and the rod are made of plastic. In this first embodiment, the stems are ultrasonically welded to the rod.
In a second preferred embodiment, the stem of each pin plug is hollow and the rod is externally threaded. A respective internally threaded brass insert is disposed in each stem for threadably engaging the rod. To permit rotating the head of at least one of the plugs by manipulating a tool, the head is formed with at least one engagement surface configured for engaging the tool. The engagement surface can be established by at least one notch.
In another aspect, a piston pin plug retainer assembly includes a rod disposable in a hollow piston pin having opposed open ends, and first and second plastic plugs affixed to opposite ends of the rod to cover the open ends of the piston pin.
In still another aspect, a method for retaining first and second plastic pin plugs in first and second ends of a piston pin includes coupling the first plug to a rod, and advancing the rod into the piston pin. The second plug is coupled to the rod. If desired, both plugs can be coupled to the rod after the rod is advanced into the pin.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts.